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The capabilities to efficiently model the transport of mass and heat in geothermal reservoirs at supercritical conditions are necessary to support the efforts to explore and utilize supercritical hydrothermal systems, as well as to extend the utilization of existing geothermal fields at greater depths, where supercritical temperatures might be encountered. Similar capabilities are needed to model the flow in wells producing supercritical fluids, possibly in a coupled way with the reservoir flow. As a step in this direction, the new EOS2H module for sub-critical and steam-like super-critical H2O-CO2 mixtures has been linked to T2Well, the extension of the TOUGH2 numerical reservoir simulator developed for the transient modeling of fully coupled wellbore-reservoir flow. The resulting code is verified against simulations performed with other supercritical reservoir simulators and steady-state subcritical and supercritical wellbore flow simulations. It is then used to perform coupled wellbore-reservoir flow simulations at the well-sector scale relevant to the conditions found in well IDDP-1, Krafla, Iceland.

The present work describes the results of a modeling study addressing the geological sequestration of carbon dioxide (CO 2 ) in an offshore multi-compartment reservoir located in Italy. The study is part of a large scale project aimed at implementing carbon capture and storage (CCS) technology in a power plant in Italy within the framework of the European Energy Programme for Recovery (EEPR). The processes modeled include multiphase flow and geomechanical effects occurring in the storage formation and the sealing layers, along with near wellbore effects, fault/thrust reactivation and land surface stability, for a CO 2 injection rate of 1 × 10 6 ton/a. Based on an accurate reproduction of the three-dimensional geological setting of the selected structure, two scenarios are discussed depending on a different distribution of the petrophysical properties of the formation used for injection, namely porosity and permeability. The numerical results help clarify the importance of: (i) facies models at the reservoir scale, properly conditioned on wellbore logs, in assessing the CO 2 storage capacity; (ii) coupled wellbore-reservoir flow in allocating injection fluxes among permeable levels; and (iii) geomechanical processes, especially shear failure, in constraining the sustainable pressure buildup of a faulted reservoir.

Injection of gas mixtures in geological structures is performed for a variety of different purposes including natural gas storage operations, CO2 flooding and Water Alternate Gas injection for Enhanced Oil Recovery, and more recently for the sequestration of GreenHouse Gases and the disposal of acid gases produced by sour hydrocarbon reservoirs. The injection of multi-component mixtures into saline aquifers and hydrocarbon reservoirs requires the understanding of the processes that govern the performances of injection wells, the fluid migration within the reservoirs, and the possible recovery of additional hydrocarbon reserves. Conventional compositional simulators employed by the oil industry, while implementing complex phase equilibrium algorithms for the hydrocarbon phases, often give only an approximate description of the aqueous phase behaviour and properties. In particular, the injection of mixtures mainly composed by acid gases such as CO2 and H2S drives pronounced modifications of aqueous phase chemical equilibria promoting water–rock reactions with possible alteration of reservoir and cap rock, as well as of wellbore cement sheaths. The gas mixtures usually injected in undersaturated conditions with respect to water, progressively vaporise the aqueous phase, concentrating the dissolved solids until they precipitate as new mineral phases, eventually reducing the initial rock porosity and permeability. Vaporised water is transported further from the injection wellbore to possibly condense again in the presence of proper thermodynamical conditions. TMGAS, a new Equation of State module for the TOUGH2 reservoir simulator, has been developed to model the injection of mixtures of inorganic gases and hydrocarbons in geological structures at conditions conventionally found in deep sedimentary basins.